Wiki info about A6M2-N

The single-seater, single-engine float seaplane fighter A6M2-N was created to cover combat operations near atolls, where the construction of airfields was often impossible.
Initially, the Kawanishi N1K1 Kyofu was planned for this purpose, but it soon became clear that Kawanishi was unable to produce the planes in sufficient quantity before the start of the war, so the navy asked Nakajima to create a float seaplane fighter. The A6M2 model 11, with non-folding wings, was chosen as a starting point. The landing gear was removed, and a large float with a built-in fuel tank installed in its place. A float was also installed under each wing for stability. The plane’s armament was left unchanged.
Despite the significantly increased aerodynamic resistance and weight, the plane was quite fast and maneuverable.
327 of these aircraft were produced, including the original prototype, but the first A6M2-Ns barely ever took part in combat, since they were destroyed shortly after arriving at Tulagi (in the Solomon Islands) in an attack by U.S. B-17s from the 11th Bombardment Group.
They were used primarily as interceptors.